ABC | Volume 110, Nº4, April 2018

Original Article Muñoz et al Atrial fibrillation ablation in valve disease Arq Bras Cardiol. 2018; 110(4):312-320 Patient eligibility criteria for AF surgery included: persistent AF of less than ten years of evolution and left atrial anteroposterior (AP) diameter at preoperative transthoracic echocardiogram in long axis view of less than 6.0 cm. 3,7 All candidates were adequately informed and signed informed consent form for the procedure, according to the local ethics committee. Fifty-three consecutive candidates who underwent valvular heart surgery were included to surgical ablation. Success of AF ablation procedure was considered when patients maintained SR at the time of discharge. All these patients were selected for initial follow up. After rhythm stabilization, which is considered to occur at least 3 months after surgery, 8 an echocardiogram was scheduled, and ambulatory 24 hour Holter monitoring and electrocardiograms were systematically performed in all candidates who remained in SR (44 patients). Holter monitoring was programmed one month after the echocardiographic study, and electrocardiograms were made during clinical visits (at least two visits during the first year of follow up). Patients with persistent AF during the first 3 months after surgery were excluded from the follow-up. Surgical technique All the procedures were carried out by full sternotomy and extracorporeal circulation. Surgical technique for cryoablationwas the same as previously described. 9 After aortic clamping, LA was opened when needed and left atrial appendage was ligated from its inside using a 3.0monofilament suture. The cryoablation probe was placed for 60 s at a temperature between –100°C and –160°C. Lines were created surrounding pulmonary veins and also joining between these circles. Three more lines were performed: between the left pulmonary veins and the left appendage, between the left pulmonary veins and the P3 portion of the mitral annulus and between the tricuspid septal valve and the inferior cava. In cases where left atriotomy was not needed (in isolated aortic interventions), high-intensity-focused-ultrasound (HIFU - Epicor) cardiac ablation was used. Epicor Medical Cardiac Ablation System (St Jude) is designed to deliver HIFU via an entirely epicardial approach and consists of an array of transducers positioned after proper sizing around the LA wall of the pulmonary vein orifices. 4 Echocardiographic study A Vivid 7 Dimension ultrasound system (GE Healthcare) was used for the transthoracic echocardiographic examination. All images and measurements were acquired with a MS4 matrix probe using the standard views according to the standards of the European Association of Echocardiography and the American Society of Echocardiography. 10,11 Strain parameters were obtained during ventricular systole (LASs – LA systolic strain) and diastole (LASa – LA diastolic strain), and strainR parameters were obtained during early (LASRe – LA strainR early) and late (LASRa – LA strainR late) ventricular diastole (Figure 1) in 2 standard echo-views (apical 4- and 2-chamber views), using speckle-tracking echocardiography to avoid the angle-dependence of DTI. 6,12 Figure 1 – Left atrial phasic functions and their relationship with the cardiac cycle. Strain and strain rate curves are shown. During left ventricular (LV) systole and isovolumetric relaxation, left atrium (LA) works as a distensible reservoir accommodating blood flow from the pulmonary veins. During early LV diastole, LA behaves as a conduit that starts with mitral valve opening and terminates before LA contraction, allowing passive emptying during early ventricular diastole and diastasis. Finally, at end-diastole, LAacts as a muscular pump contributing to LV filling with active atrial contraction. (LASs: left atrial systolic strain; LASa: left atrial diastolic strain; LASRe: early left atrial strain rate; LASRa: late left atrial strain rate). LASs LASa LASRe LASRa CONTRACTION CONTRACTION RESERVOIR CONDUIT 313